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.\" Common Development and Distribution License ("CDDL"), version 1.0.
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.\" 1.0 of the CDDL.
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.\" Copyright 2015 Joyent, Inc.
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.Dd May 11, 2016
.Dt PSYSENTRY 3PROC
.Os
.Sh NAME
.Nm Psysentry ,
.Nm Psysexit
.Nd set system call entry and exit actions
.Sh LIBRARY
.Lb libproc
.Sh SYNOPSIS
.In libproc.h
.Ft int
.Fo Psysentry
.Fa "struct ps_prochandle *P"
.Fa "int which"
.Fa "int stop"
.Fc
.Ft int
.Fo Psysexit
.Fa "struct ps_prochandle *P"
.Fa "int which"
.Fa "int stop"
.Fc
.Sh DESCRIPTION
The
.Fn Psysentry
and
.Fn Psysexit
functions controls what actions the process handle
.Fa P
should take upon executing a system call.
.Pp
The system allows a process to be stopped on both entry and exit of a
system call.
For information on the state of the process when it is stopped due to system
call tracing, see the
.Sy PCSENTRY
and
.Sy PCSEXIT
sections of
.Xr proc 5 .
.Pp
The value of the
.Fa stop
parameter controls whether or not the system call listed in
.Fa which
causes the process to stop.
A value of non-zero indicates the process should stop;
a value of 0 indicates it should not.
.Pp
The value of
.Fa which
indicates which system call the change applies to.
A value of 0 applies to all system calls.
Note, the system does not supply a stable mapping from system call names to
identifiers.
.Pp
These functions only apply to actively running processes.
They do not function on handles that refer to core files, zombie processes,
or ELF objects.
.Sh RETURN VALUES
Upon successful completion, the
.Fn Psysentry
and
.Fn Psysexit
functions return the previous disposition of the system call --
.Sy 0
if it was not set to stop and
.Sy 1
if it was --
and the system call state is updated.
Otherwise,
.Sy -1
is returned,
.Dv errno
is updated with the error that occurred, and the system call state is
not updated.
.Sh ERRORS
The
.Fn Psysentry
and
.Fn Psysexit
functions will fail if:
.Bl -tag -width Er
.It Er EINVAL
The value of
.Fa which
is invalid, e.g. it is less than zero or greater than the largest defined
system call.
.It Er ENOENT
The handle
.Fa P
refers to a process that is a zombie, a core file, or an ELF object.
.El
.Sh INTERFACE STABILITY
.Sy Uncommitted
.Pp
Note, while the
.Fn Psysentry
and
.Fn Psysexit
functions are uncommitted, the mapping of system calls to system call
numbers is
.Sy Not-an-Interface
and may change at any time.
.Sh MT-LEVEL
See
.Sy LOCKING
in
.Xr libproc 3LIB .
.Sh SEE ALSO
.Xr libproc 3LIB ,
.Xr proc 5 ,
.Xr attributes 7
